Thursday, October 22, 2015

Plant Growth Hormone - Ethylene

Ever throw away a brown banana which seemed to have been green just yesterday? Was the banana part of a bunch? Were there any tomatoes or apples on your counter by the banana?
Augustus Binu [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons


The culprit, in that case, is ethylene, a phytohormone. Yes, just like animals, plants have hormones that control growth, development and stress perception! Ethylene is a simple molecule composed of 2 carbons attached via a double bond and sandwiched between 4 hydrogens (H2C=CH2).
Ethylene chemical structure Public Domain, Ben Mills posted on Wikimedia
So how does such a simple molecule make bananas become brown and mushy? Same way all developmental changes occur, through changes in gene expression! Ethylene is simply the signal molecule and perceived from both internal and external sources. It can be volatilized, aka become a gas, and is involved in a wide range of processes from germination and growth to fruit ripening and abscission, even playing a role in gravitropism and stress response. Scientists have been studying ethylene for over 100 years. It was first described in 1901!

In most fruits, ethylene is the primary hormone that guides ripening. In the case of our banana, they are actually picked green and then exposed to large quantities of ethylene gas to ripen them artificially so they all ripen at the correct time to go to market. Inside the banana's cells, ethylene binds to specialized receptors (ETR1) that are found on the cell membranes. 

While one often thinks about gene regulation being based on positive interactions, a hormone binds and turns something on, ethylene binding to the receptor actually deactivates this receptor! Without ethylene, the receptor is keeping CTR1 activated so that it keeps the downstream proteins inactive. When ethylene binds, it turns the receptor off so that CTR1 is no longer activated and EIN2 can then stabilize the EIN3 transcription factor which activates ethylene responsive genes.
Ethylene regulatory network, personal illustration, based on Shi et al 2012  model

For our banana, going from a hard, green, bitter unripe banana to a soft, yellow, sweet ripe banana requires a plethora of genes from many pathways. In fact, a study showed that over 100 pathways were involved in ripening. These genes are responsible for softening the tissue, changing starch to sugar, production of aromatics, and more. Next time you take a bite of your ripe banana, remember the importance of ethylene and how many genes were involved to make this perfect bite!

References:

Alexander and Grierson, 2002  J. Exp. Bot. 53 (377): 2039-2055. doi: 10.1093/jxb/erf072 http://jxb.oxfordjournals.org/content/53/377/2039.full 
Asif, M., et al, 2014. BMC Plant Biol. 14: 316.  doi:  10.1186/s12870-014-0316-1 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263013/
Shi Y, et al., 2012. Plant Cell 24 (6):2578-2595. doi:10.1105/tpc.112.098640 http://www.plantcell.org/content/24/6/2578
Wikipedia. Ethylene  https://en.wikipedia.org/wiki/Ethylene

Wednesday, August 26, 2015

Mighty Titan!

Currently the web is abuzz about the once a decade blooming of the so-called corpse flower, Amorphophallus titanum (Titan arum). Not only is it rare, the corpse flower only blooms once every 7 - 10 years, it is HUGE! While it looks like one giant flower, it is actually a group of flowers on the large stem. In botany, we call this an inflorescence. And Titan arum has the largest unbranched inflorescence known on this planet measuring, on average, 6 feet tall, with the record over 11 feet, and can be well over 100 pounds.

Credit: US Botanic Garden, Public Domain
The corpse flower moniker has stuck with these giants as they emit a foul stench that smells of rotting flesh. What's a gorgeous flower like that doing smelling so pungent?

The answer, looking for hot dates with carrion-eating insects, of course! The stinky chemicals wafting off the inflorescence attract these insects with the promise of a rotting flesh buffet. Both male and female flowers are found on the inflorescence stem of Titan arum. On the first night that the large spath (the funnel looking piece) is open, the female flowers bloom and will hopefully be pollinated by the insects attracted to the stench. On the second night, the male flowers bloom where the attracted insects pick up pollen. The fact that the female and male flowers open on back to back nights cuts down the potential for self pollination.

In addition to the foul stench, this particular flower is also capable of raising its internal temperature above that of room temperature! This warming up is another attractant for the pollinators, as the heat increases when the flowers are blooming and insects are cold blooded. But how is this heat generated?


To answer this question, lets delve a little into some biochemistry. As I've said before, plants are the world's best biochemist and this is certainly one of their cooler processes. For heat-producing plants, this temperature increase is due to the action of a single enzyme: alternative oxidase.

Alternative oxidase is found in the mitochondria, where cellular energy is produced. During normal cellular respiration (the process by which energy is created), electrons pass through several different enzyme complexes inside the mitochondrial membrane, creating a proton gradient which then drives ATP (energy) generation. When thermogenessis is required, alternative oxidase interrupts this process, absorbing electrons and releases heat. During flowering, almost all of the electron energy that enters the mitochondria is passed through alternative oxidase into heat. The triggering of the alternative oxidase pathway is thought to occur via 2 ways, which may be exclusive or occur simultaneously. 1) the alternative oxidase present in the cell is activated by the breakage of a disulfide bridge within the enzyme and/or 2) the amount of alternative oxidase present in the cells increases. Either way, a plant that can control when it warms up is very impressive.

There is a lot of attention on the corpse flower right now as many of these giants have been in bloom recently. Today, I know they are waiting anxiously at Chicago Botanic Garden ("Spike"), Binghamton University, and Virginia Tech for ones to bloom. Last week, "Stinky" bloomed at Denver Botanic Garden who actually sent some pollen to Chicago to pollinate "Spike"! Earlier this year, the Royal Botanic Garden of Edenburgh's Titan bloomed with its own Twitter account: @TitanArumRBGE. The size, rarity, and biochemical prowess of the flower results in a well deserved, standing room only reception. If one is blooming near you, get out to see, and smell, this impressive plant.

References
http://www.chicagobotanic.org/titan_arum_corpse_flower

http://news.nationalgeographic.com/news/2003/07/0718_030718_stinkyflower.html

https://en.wikipedia.org/wiki/Amorphophallus_titanum

http://www.edenproject.com/learn/for-everyone/plant-profiles/titan-arum

http://www.bbc.co.uk/nature/life/Titan_arum#p004gx80 (with video of Sir David Attenbrough!)

Korotkova, N., & Barthlott, W., 2009. On the thermogenesis of the Titan arum (Amorphophallus titanum). Plant Signaling & Behavior, 4(11), 1096–1098. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2819525/


Wagner AM1, Krab K, Wagner MJ, Moore AL., 2008. Regulation of thermogenesis in flowering Araceae: the role of the alternative oxidase. Biochim Biophys Acta:993-1000. http://www.sciencedirect.com/science/article/pii/S0005272808000881


Saturday, July 4, 2015

America's Autotrophs

Here in the US of A, it is Independence Day, the birthday of the country. Everyone is familiar with the flag, the Eagle, the Uncle, the music of America.. but where are the plants in all of this?! So today, in honor of America's birthday, I present her autotrophs (self feeder, aka plants)!

While the Bald Eagle was chosen to represent America in 1782, the first autotroph to represent her was the national flower which was not chosen until 1986. It took more than 200 years for America to pick a plant. The national flower, signed into existence by President Ronald Regan, is the Rose.
A rose in a flower arrangement - personal photo
Why the rose when it is, mostly, an introduced species? A few reasons. There is a beautiful rose garden at the White House. George Washington created a rose cultivar. It was brought over by some of the early colonists from Europe to America. I suppose this makes it a decent symbol, as it is as much a part of North America, as the colonists who founded the country. I still would rather have seen a native autotroph... thankfully America fixed that mistake with the national tree.

Oak - personal photo

The national tree was designated in 2004 via popular vote. The mighty Oak was declared the winner by a landslide. Oaks have several things in their favor for being the national tree of the USA. First, their genus name Quercus is incredibly fun to say! Next, there are over 90 native oaks in the US, almost every state has some type of native oak tree! The wood from oak trees were used to make log cabins as settlers moved west, create ships for commerce and war, and make very good wine barrels. And lastly, Oak gives me one of my favorite lines to spout from M*A*S*H.

Bet you don't know what kind of wood this is?
Oak
Nope, it's oak!
Oaks are angiosperms, meaning they are flowering plants. The male flowers look like little tendrils dripping down and dumping pollen upon unsuspecting allergy sufferers every spring. This design is helpful as it allows the pollen to be blown around to other branches and other trees where it can come in contact with the female flowers. These female flowers, once fertilized, will turn into acorns. The diagram below is from the white oak (Quercus alba).
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 1: 622.

Oak leaves can be lobate, as seen in the white oak above, serrated, or smooth. These leaves will turn beautiful colors in the fall and then, often, remain on the tree, dead, until spring. Oak bark is very rough, and often furrowed (grooves). If you ever want to try and key out a particular oak species use this very detailed Flora of North America oak key.

So, there we have America's Autotrophs. As you go out tonight, you can tell all your friends as you watch the fireworks what tree and flower represent the nation. So far, none of my friends have been able to correctly guess (though they all got the eagle!), let me know if you have better luck with yours!

References
http://nationalrosegarden.com/the-national-flower/
http://forestry.about.com/od/treeandforestcelebration/a/oak_us_tree.htm
http://plants.usda.gov/core/profile?symbol=QUAL

Friday, July 3, 2015

Child Care Issues

One of the hardest parts about being a single Mom is finding and affording child care for Boo. At least with 2 parents there is the potential for sharing the "babysitting" duties without it breaking your pocket book. For me, it's either me or hiring someone. Closest family support is 2 hours away, which could be a lot worse, but does not help much in the day to day. If Boo is sick, I'm taking the day off. If school is closed cause of snow day, I'm home. Going out with friends is confined to breaks when Boo visits his dad and I do not have to worry about who will take care of my child and/or how can I afford dinner out + babysitting. If something gets off schedule in the lab, I can't stay and fix/finish it because I have to leave to fetch Boo by X time.
Disney's Treasure Planet

For the last two years, he was in a public, large group setting after school situation and it was not very good for him. I kept him there because it was cheap, convenient, and he kinda liked it. But due to some issues, that is no longer an option for the next school year which has left me in a bind and added a great deal of stress to my life. The uni I'm attending does not have after school age care, they do provide infant/preschool at a slightly reduced rate for students (and even then it's the most expensive option in town), but nothing for older kids. The only other group child care place in the area is very expensive. Not to mention when I visited it, the place was really old, run down, and felt crowded with all the kids in a small place. It really did not feel like a good place to take him. So that leaves two options: A) leave lab at 2:30 every day to pick him up from school, or B) hire a private caregiver to pick him up and take him home until I get back.

Obviously A would cut into my research hours, to the tune of 2 hours a school day or 10 hours a week. It also is impossible the days that I teach as afternoon labs go until 4:20pm. It would be much cheaper (aka free!), and honestly, I think Boo would be much happier as he already complains about how little time we are together (which is already a source of Mommy guilt itself). But it is not likely to happen, which leaves option B.

Option B has it's own pitfalls. First and foremost, I have no idea how to even find a private caregiver. Sure I could look online, put an ad in the campus classified, but what do I really know about anyone from these sources? This is my only child we're talking about, I'd feel better if I could find someone I, or someone I personally know and trust, recommended. Plus, what if they can't make it! Having someone come to your house is not like a corporation where a substitute will be assigned if someone is sick/accident/whatever, if something happens to private caregiver, I have to figure out how to get home quickly. Secondly, private care is not cheap. 2 days of private care will probably cost what one week of group used to cost me. And ideally, I would use it 4 days a week. So we are looking at doubling my child care costs. Grad student budgets are already tight, doubling any of my expenses is not an easy feat to accomplish. How will I pay for this? I have no idea. Which loops me back to, is there any humanly possible way to return to option A? Or is there an option C I have yet to discover?

I wish I had answers. I do know it would be easier for me if my uni had after school care that was affordable. I do know it would be easier if I wasn't alone. I do know it would be easier if Boo could be trusted to hang out at my desk for more than 10 minutes without getting in my way so I could work with him around. I do know I'm not the only one struggling with finding affordable childcare. Now if we could only figure out how to fix it.

Monday, June 22, 2015

Colorful Carotenoids


One of my professors once said (ok I lied, he actually says this all the time), “Plants are the world’s best biochemists.” And it is very true. Plants produce thousands of different types of phytochemicals, including pigments, toxins, hormones, signaling molecules, the list goes on and on. This is going to be the first in a series called “Best Biochemists” where I’ll highlight different plant produced chemicals. Today’s post is going to scratch the surface of the beautifully colored carotenoids.
Fall Leaves - personal photograph
Carotenoids are probably most well-known by the yellow-orange-red color they provide to fruits, vegetables and flowers, for example the orange in carrots, red in tomatos, or yellow in peaches. They are a huge family with over 600 naturally occurring carotenoids. Most of the coloration, fragrance, and even taste of many flowers and spices come from carotenoids. The bright oranges, reds, and yellows that paint the leaves of trees is due to a build-up of carotenoids as photosynthesis ceases. So where does all of this diversity come from? Biochemically, all carotenoids start as a 40 carbon chain called phytoene.

"Phytoene" by Edgar181. Own work. Licensed under Public Domain via Wikimedia Commons.
 Phytoene is colorless and requires 4 dehydrogenation (loss of hydrogen) and 2 isomerization (rearrangement) reactions to become lycopene, the first colored carotenoid. Lycopene is bright red and gets its name from Lycopersicum, the genus name of tomatoes. Most of the bright red fruits and vegetables we eat are high in lycopene, such as tomato, watermelon, pink grapefruit, red bell peppers, etc. Lycopene is an important branchpoint in carotenoid biosynthesis as in the next step, the ends of lycopene are cyclized (made into rings). These rings can be in several different configurations, the most famous of which is the beta ring, that forms both ends of beta-carotene.

"Beta-Carotin" by NEUROtiker. Own work. Licensed under Public Domain via Wikimedia Commons.
Carotenes are very important to humans as precursors of Vitamin A. Beta-carotene is the most important for this purpose as it is composed of 2 Vitamin A (retinol) molecules linked tail to tail. Alpha and gamma carotene both contain 1 Vitamin A linked to a different ring type (epsilon). Thus, for every molecule of beta-carotene we consume, 2 Vitamin A molecules are produced during digestion, while only 1 is produced by alpha and gamma-carotene. The most famous usage of Vitamin A is in our eye health and development. This is where the idea that eating carrots can increase your night vision originates.  

Obviously, plants do not require Vitamin A for their eye development, so why do plants produce carotenes? All of the carotenoids are produced inside the plastids of plant cells; the most famous plastid is the chloroplast. Chloroplasts are the site of photosynthesis within plants. Inside the photosynthetic apparatus, we find 12 beta-carotenes in photosystem II and 22 beta-carotenes in photosystem I. There they, and all the carotenoids, act as extra light receptors, collecting light at wavelengths that chlorophyll cannot. In addition to capturing light, beta-carotene is a powerful antioxidant. It quenches highly reactive oxygen species that are generated as a by-product of photosynthesis to protect the photosystems. For example, beta-carotene in photosystem II acts as a backdoor for the energy contained in singlet oxygen’s away from the reaction core D1/D2 proteins and into cytochrome b559 cycle electron transport so that the reaction core is not damaged and the energy is not lost.
Beta-carotene backdoor - my silly diagram work
Beta-carotene and alpha-carotene, while used in these forms, are also critical steps in the production of xanthophylls. Xanthophylls are oxygenated carotenoids and appear yellow in coloration. The most common xanthophyll is lutein, which is found in high concentrations in kale and spinach. Lutein is also important for our vision, in our retina it prevents oxidation of lipids and proteins. In plants, lutein quenches damaging reactive oxygen species produced during photosynthesis.

Light capture and antioxidant properties are only a few of the functions of carotenoids. All of the carotenoids can be cleaved at any double bond to produce a wide array of apocartenoids (less than 40 carbon chains) which are found in the fragrances, tastes, and colors of various spices in the world. The interconversion of several forms of xanthophylls play an important role in the state transitions of photosynthesis, a feature called non-photochemical quenching. Plant hormones, such as abscisic acid are formed from carotenoid precursors.

Clearly, carotenoids are too diverse of a group to be summed up in one post. Thus look for future Best Biochemists posts to delve into the apocarotenoids, xanthophyll state transition, and phytohormone formation.


References

Moise, A., Al-Babili, S., and Wurtzel, E., 2014. Mechanistic Aspects of Carotenoid Biosynthesis. Chemical Review 114(1):164-193.  http://pubs.acs.org/doi/abs/10.1021/cr400106-y (paywall :( )
Telfer, A. 2002. What is beta-carotene doing in the photosystem II reaction centre? Philosophical Transactions Royal Society of London B Biological Sciences 357(1426):143-139 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1693050/

Monday, June 15, 2015

Drought Resistant Plants?

Water is an essential component to life on this planet. Dehydration is a serious problem; complete lack of water will kill an adult human in only 3 days. Plants also suffer from dehydration, which can also lead to their death, but more important to agriculture is the loss in seed yield. Susceptibility to dehydration varies between plants, for example, cacti store water and thus can go a very long time without water, while impatiens require frequent watering. Drought, lack of water, is occurring worldwide. Right now California is, and has been, experiencing an exceptional drought. In 2014, 5% of the irrigated cropland and over $1 billion in direct agriculture was lost. That's just the losses in one year for one state, imagine the losses worldwide if droughts continue to spread.

Scientists have been studying drought tolerance properties in plants for decades with the hope of being able to translate the knowledge into drought resistant crops. And this month, a new transcription factor was described that might play a major role in regulating drought tolerance (Sakuraba, 2015). A transcription factor is a protein that binds to DNA to activate specific genes, they are the middle men of the cell, passing a signal to activate the work force. When new environmental condition arises, cells need to change the genes that are expressed rapidly and this is accomplished by transcription factors. Once they are activated, transcription factors then activate a suite of genes which produce the proper proteins for survival. This particular transcription factor is designated NAC016. The NAC family of transcription factors is one of the largest known in plants, with 106 NAC genes in the Arabidopsis (the study organism and model species for plant research) genome.

The levels of NAC016 were measured in a variety of abiotic stressors in wild type (aka normal) Arabidopsis by researchers in Dr. Nam-Chon Paek lab at Seoul National University. They found that these levels increased dramatically only during dehydration, not under cold or heat stress which suggested that this transcription factor plays a role in drought tolerance. To fully characterize NAC016, the researchers used two different mutants, a knockout (nac016) which has a non-functional NAC016 and an overexpressor (NAC016-OX) which expresses NAC016 at a very high level regardless of external conditions. After dehydration for 2 weeks, all 3 lines were compared and only the nac016 knockout had a high survival and recovery rate. Additionally, they looked at seedlings moved to dry filter paper and after 12 hours the nac016 again were fine while the other two lines were wilted. All of this means that the loss of NAC016 results in more drought tolerance!


Arabidopsis wild type and nac016 mutant after drought stress. Photo credit: Nam-Chon Paek, Copyright ASPB.

How does this work? The loss of NAC016 resulting in an increase of drought tolerance means that NAC016 is a negative regulator. It depresses the genes required for successful drought survival. The researchers examined several different genes known to be important for drought tolerance and indeed they were increased when NAC016 was knocked out and decreased when NAC016 was increased. One important pathway that NAC016 impacted was that of the hormone abscisic acid, which controls water retention via stomata (little pores on the leaves) opening/closing. Preventing water loss out of the stomata is an important defense against dehydration.

So... why care? Right now, this has only been shown in Arabidopsis. Arabidopsis is the model plant species because it is small, has a quick reproduction time, and has a fully sequenced genome. Most plant research begins in Arabidopsis and then is applied to other species. If NAC016 is shown to be a negative regulator of drought tolerance in agriculturally important species, then that's a target to remove. This removal can be done either by transgenic knockout, RNA interference, or traditional breeding techniques. But none of these avenues can be taken until the targets are established and this paper is a great first step towards identifying these targets.


References
Sakuraba 2015: http://www.plantcell.org/content/early/2015/06/09/tpc.15.00222.abstract
ASPB Press release w/ photo  https://c.ymcdn.com/sites/aspb.site-ym.com/resource/group/6d461cb9-5b79-4571-a164-924fa40395a5/PressReleases/061115_PressRel_Sakuraba.pdf
http://www.drought.gov/drought/
http://news.ucdavis.edu/search/news_detail.lasso?id=10978

Monday, June 8, 2015

Giant Kelp

As today is World Ocean Day, I thought I would feature a post about one of my favorite algae, the giant kelp, or more scientifically Macrocystis pyrifera. I learned to SCUBA dive in the kelp forests of Southern California. I have many, many fond memories of fining my way through the fronds. The way the light filters through the blades, the gentle swaying of the stalks, the many creatures darting around, was the epitome of peaceful.
My best pic of kelp, I haven't been back since digital cameras :(
Giant kelp gets its common name because it truly is giant, it can be 150 feet long and grow almost 2 feet a day! Kelp forests are so large they can be seen from space. In fact, Floating Forests takes advantage of this fact by using volunteers to mark the location of kelp in satellite imagines, it's a great little citizen science project which I reviewed here.

The pneumatocysts at the bottom of each blade resulted in the genus name Macrocystis as it means "large bladder." One of the characteristics that distinguish giant kelp from bull kelp or other large brown algae, is the single pneumatocyst found at the end of every single blade. These bladders are full of gas to keep the algae floating in the water column and closer to the sunlight needed for photosynthesis. Looking like a giant tangled knot of roots at the bottom of the kelp is the holdfast. Holdfasts do just what the name implies, hold tight so that the algae is not dislodged in rough conditions, they do not absorb water or nutrients like roots do for land plants. 

Another ancient film photo, this one featuring CA state fish the Garibaldi
Kelp forests resemble the forests you've probably hiked through since they are the base of a large food web, providing both food and habitat. They create a vertical environment, with different species of fish, invertebrates, algae, and even marine mammals inhabiting the various levels. They can be found in the holdfasts, living in the fronds, playing in the canopy. Sea otters have been known to wrap themselves in the canopy to keep themselves in position while sleeping. Encountering macrofauna such as seals, sea lions, giant sea bass, or sharks was common for me when diving the Channel Islands kelp forests, but my favorites were the tiny creatures. Staring closely at the rocks and kelp to find little invertebrates hiding in the fronds/holdfast or fish that mimic the kelp, all of which is easily missed when swimming past, was always exciting for teenage me. Not only do they provide habitat on the shore, when the holdfast breaks down, floating kelp mats bring their nutrients and hitchhikers out to the open ocean where they attract pelagic fish and birds.
 
Giant kelp is harvested and used to make algin, a thickening agent which is found in a lot of food. It also has been used for fertilizer, gun powder, in cosmetics and many other applications. In California, harvesting kelp is a $40 million dollar industry. To protect the kelp forest environment, only the kelp found in the top 4 feet of the water column are collected, leaving the bulk of the strand in tact to regrow. In addition to harvesting, kelp forests provide other economical advantages to the coasts they cover, such as tourism. Another important feature is shoreline protection, waves are slowed down by the thick kelp forests and thus less energy hits the shore, resulting in less erosion.
Last old scanned, film photos of the kelp forests, this time looking up!

To experience a small taste of the diversity of the kelp forest, Monterey Bay Aquarium features a Kelp Cam in their big kelp forest tank here, as does Scripps Birch Aquarium here.


References
http://aquarium.ucsd.edu/Education/Learning_Resources/Voyager_for_Kids/kelpvoyager/index.html
http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/climate-change/macrocystis-pyrifera/index.html
http://www.mbari.org/staff/conn/botany/browns/james/default.htm
 http://sanctuaries.noaa.gov/about/ecosystems/kelpdesc.html
http://www.westcoast.fisheries.noaa.gov/habitat/habitat_types/kelp_forest_info/about_kelp_forest.html

Tuesday, May 26, 2015

Yellow Oxalis


I was weeding in my back patio area with kiddo this week when I found a flower I remember fondly from my childhood. We always called them lemon flowers, they were everywhere around the pond at our apartment when I was a kid. Giddy that I had found them, I called Boo over and showed him the little yellow flowers. My mom had always called them lemons flowers, why did he think they were called that? Obvious answer, because they are yellow. Good guess! But then I told him to eat the little yellow flower, to which I received a rather skeptical look. I assured him it was ok and so he popped the petals into his mouth. “It’s sour like a lemon too! Can we let those grow? Don’t weed them!” So I left them alone as I both enjoy the way they look and taste.

Personal image from the backyard
The botanist in me wondered what was the proper name of these little yellow flowers, surrounded by what looked like clover leaves. It took a some searching but I discovered these flowers are Oxalis stricta L. commonly called yellow oxalis, yellow woodsorrel or lemon clover (so my Mom was close on her common name). They are edible and very refreshing! In fact, they are not a bad source of vitamin C. In 100 grams of yellow oxalis there is 59 milligrams of Vitamin C. In comparison, 100 grams of clementine oranges has 48.5 milligrams. That’s a little over 17% more Vit C in these common field flowers. The sour, tangy, lemon-like flavor is caused by the Vitamin C and Oxalic acid content. While I love munching on them when out and about, be aware that, as with many things, a large amount of oxalic acid can be toxic and you should not eat these if you have a kidney disorder. The leaves and flowers can add a nice zing to your salad, the leaves and stems can be juiced to get an acidic juice (like vinegar), and the whole plant can be boiled and used as orange dye.

Now one should not go out and eat any shamrock-esque leaves or yellow flowers that they encounter. How do you know that you have found a grove of yellow oxalis? Here are a few things you can use to identify it. The leaves are composed of 3 heart-shaped leaflets, which fold up at night or during abiotic stress, such as heat. The yellow flowers have 5 petals, 5 sepals (the green part of the flower), 10 stamens (produce pollen/sperm) and a single pistil (contains ovary). It will produce flowers all spring/summer long. A long root connects many different vegetative clumps, which is one of the reasons this plant does so well in the cracks of sidewalks. The root can spread along the crack and send up lots of sprouts. The seed pods have 5 ridges and a pointed top. 
"6h common yellow oxalis" by 6th Happiness - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons
According to the USDA Plants database, yellow oxalis is native to 44 of the lower 48 states of the United States and invasive in all but 1 southern Canadian province. So if you are in the US/S Canada and not in Alberta, Oregon, California, Nevada or Utah, you should be able to find some yellow oxalis around. They like most growing conditions and spread rapidly, which has led to them often being considered a weed in ornamental planting areas (lawns/gardens). Next time you come across them, instead of just weeding them away, give the flowers a little taste (those are my favorite part!). If you do want to eliminate them, but sure you get the entire root system, otherwise the root remaining will just send up another shoot. Personally, I’m cultivating a little garden in the corner of our yard which I’m hoping will be full of yummy flowers for us all summer long.


References